Abstract

In this mini-review, we focus on essential and semi-essential amino acid concentrations in plasma as potential biomarkers for clinical consequences related to protein malnutrition. In Japan, protein malnutrition is common across varying populations, especially in elderly adults and young women, which could cause increased risk of sarcopenia, heart failure, impaired immune response, and conditions specific to women. After establishing clinical reference intervals for plasma free amino acid concentrations, we have reported the clinical characteristics of a Japanese subpopulation with low plasma free essential and semi-essential amino acid concentrations (Low-EAA), which we hypothesized to be potential protein malnutrition. Intriguingly, the ratio of the subjects with Low-EAA was varied depending on age and gender, with elderly subjects and young women having higher ratio of subjects with Low-EAA. After adjusting for age, sex, and BMI, Low-EAA was significantly associated with surrogate markers of protein malnutrition, anemia, cardiovascular diseases and infectious diseases. Plasma free amino acid concentrations could be not only a potential biomarker, but also a predictor for health problems associated with malnutrition.